1. Field of the Invention
The present invention is related to a transmission band limiting filter apparatus and a transmission apparatus. More specifically, the present invention is directed to a transmission band limiting filter and the like, which are used to execute a transmission band limiting process operation of transmission data for a portable telephone and a base station system.
2. Description of the Related Art
In a wireless mobile communication system, more particularly, in a cellular portable telephone system, a multiple access system is used in order to simultaneously establish communications between a base station and a plurality of mobile stations (communication terminals). In this multiple access system, a base station and/or plural mobile stations access empty wireless lines so as to establish wireless communications. This multiple access system is mainly subdivided into a frequency division multiple access (FDMA) system, a time division multiple access (TDMA) system, and a code division multiple access (CDMA) system. Then, a base station allocates such a multiple access parameter corresponding to a multiple access system employed in a relevant wireless communication system with respect to a mobile station.
In the FDMA system, a plurality of channels are formed by varying the frequency. In the TDMA system, a plurality of channels are formed by slightly shifting time. To the contrary, in the CDMA system, while all of the frequencies and time are used, since the channels are discriminated from each other based upon the specific codes transmitted with being multiplexed on the signals, there are such drawbacks that the frequency components would be broadened, the frequency utilizing efficiency would be lowered, and thus, the broad band line should be used. However, this TDMA system may own such a feature that since the codes are multiplexed to convert the signals, the high secrecy characteristic could be maintained. Therefore, this TDMA system has been widely used.
On the other hand, in the CDMA system, in particular, while a multiplexing process operation is carried out, there are certain possibilities that a large current instantaneously flows. A so-called xe2x80x9climiter functionxe2x80x9d capable of limiting transmission power may constitute a major important factor in this CDMA system.
Conventionally, a transmission apparatus equipped with a peak amplitude suppression function is disclosed in, for example, Japanese Patent Laid-open Patent No. Hei(JPA)-9-18451.
As indicated in FIG. 24, a transmission band limiting apparatus employed in such a CDMA system that while a spread spectrum communication system is employed, a plurality of users are stored within the same frequency band, is constituted by a transmission data input dynamic range limiter processing unit 2401, and also an n-times oversampling ROF unit 2402. The transmission data input dynamic range limiter processing unit 2401 limits an amplitude of multiplexed data. The n-times oversampling ROF unit 2402 samples the output data of this transmission data input dynamic range limiter processing unit 2401, and cuts off such output data having a large amplitude.
First, the transmission data which are multiplexed and are entered from an input terminal xe2x80x9cidataxe2x80x9d and another input terminal xe2x80x9cqdataxe2x80x9d are inputted into the transmission data input dynamic range limiter processing unit 2401. Then, this transmission data input dynamic range limiter processing unit 2401 performs the input dynamic range limit with respect to such input transmission data having a value larger than a preset value, so that the maximum value of the transmission data is suppressed.
Next, the transmission data whose maximum value has been suppressed by the transmission data input dynamic range limiter processing unit 2401 is entered to the n-times oversampling transmission band limiting filter unit 2402 so as to be processed by the transmission band limiting process operation thereof. Then, the transmission data which have been processed by the band limiting process operation by the n-times oversampling transmission band limiting filter unit 2402 are transferred via an output terminal xe2x80x9cioutxe2x80x9d and another output terminal xe2x80x9cqoutxe2x80x9d to a post stage.
On the other hand, as shown in FIG. 25, the transmission data which has been processed by the band limiting process operation by the n-times oversampling transmission band limiting filter unit 2402 is further processed by an instantaneous peak suppression processing unit 2503 so as to suppress an instantaneous peak of this transmission data. The above-described apparatus has been proposed. Similar to the first-mentioned apparatus shown in FIG. 24, in this apparatus, transmission data which are multiplexed and entered from an input terminal xe2x80x9cidataxe2x80x9d and another input terminal xe2x80x9cqdataxe2x80x9d are inputted into a transmission data input dynamic range limiter processing unit 2501. This transmission data input dynamic range limiter processing unit 2501 performs an input dynamic range limiting operation with respect to such input data having a value larger than a set value in order to suppress the amplitude of the transmission data.
Next, the transmission data whose maximum value has been suppressed by the transmission data input dynamic range limiter processing unit 2501 is entered to an n-times oversampling transmission band limiting filter unit 2502 so as to be processed by the transmission band limiting process operation thereof. Then, the transmission data which has been processed by the band limiting process operation by the n-times oversampling transmission band limiting filter unit 2502 produces a peak value different from such a peak value which is suppressed by the peak value producing factor owned by the n-times oversampling transmission band limiting filter unit 2502, although the amplitudes of the transmission data have been suppressed by the transmission data input dynamic range limiter unit 2501. As a consequence, with respect to the transmission data outputted from the n-times oversampling transmission band limiting filter unit 2502, the processing unit 2503 equipped with both the transmission power detection function and the instantaneous peak suppression function suppresses both an instantaneous peak and a peak value of such a signal having a value larger than the value which is again set. Next, the data outputted from this processing unit 2503 are transferred via the output terminal xe2x80x9cioutxe2x80x9d and another output terminal xe2x80x9cqoutxe2x80x9d to the post stage.
In the transmission control system shown in FIG. 24 arranged by the transmission data input dynamic range limiter unit 2401 and the n-times oversampling transmission band limiting filter unit 2402, in such a case that the transmission power variation in the time axis by the transmission data entered into the input terminals xe2x80x9cidataxe2x80x9d and xe2x80x9cqdataxe2x80x9d represent such a large fluctuation characteristic as indicated in FIG. 17, the band limiting process operation (limiting process) is carried out by the transmission data input dynamic range limiter unit 2401 in response to the set limited value. As a consequence, while the instantaneous peak value is suppressed and the upper limit value of the transmission power variation is removed (see FIG. 18), such transmission data having no transmission power variation can be obtained.
However, in the case that the transmission data which has been limiter-processed by the transmission data input dynamic range limiter unit 2401 is inputted into the n-times oversampling transmission band limiting filter unit 2402, the transmission power variation again owns such a characteristic having a high instantaneous peak, as indicated in FIG. 19. Although the instantaneous peak of the transmission power variation has been suppressed as illustrated in FIG. 18, another instantaneous peak value which is caused by a different occurrence factor would occur. This instantaneous peak value is caused by the convolution process operation with respect to both the impulse response characteristic and the transmission data stream owned by the n-times oversampling transmission band limiting filter unit 2402. Therefore, there is such a problem that this instantaneous peak value would occur irrespective of the input transmission data.
On the other hand, in accordance with the transmission power control apparatus shown in FIG. 25, the instantaneous peak value produced by the n-times oversampling transmission band limiting filter 2502, which causes the above-described problem in the transmission power control apparatus of FIG. 24, may be suppressed to such an arbitrary amplitude set by the processing unit 2503. The transmission power control apparatus is constructed of the transmission data input dynamic range limiter unit 2501, the n-times oversampling transmission band limiting filter 2502, and the processing unit 2503 equipped with both the transmission power detecting function and the instantaneous peak suppressing function. As represented in FIG. 20, the transmission power variation may have such a power characteristic having no variation with respect to the time axis. An ordinate of FIG. 20 indicates a transmission power variation, while an abscissa of FIG. 20 denotes transmission time. However, this amplitude suppressing method may cause the suppression adverse influence, so that this adverse influence is left in the transmission data as the nonlinear distortion of the amplitude component in the time axis, and as shown in FIG. 21, the frequency characteristic of the transmission data, which is obtained by the band limiting process operation, is broadened around the band, so that the frequency characteristic would be considerably deteriorated, resulting in another problem. FIG. 21 represents a gain (dB) in the case that the frequency peak is set to a center of the abscissa thereof.
The present invention has been made to solve the above-explained problems, and therefore, has an object to provide such a transmission system capable of effectively suppressing an instantaneous peak value of transmission electric power required to transmit data, and also capable of transmitting data, while reducing distortions and also maintaining a better frequency characteristic. In other words, an object of the present invention is to constitute such a transmission system operable in a high efficiency and low power consumption, while a region capable of compensating for a linearity of an amplifier can be made small.
The present invention has been made to solve the above-explained problems, and is featured by arranging a correcting unit at a prestage of an ROF unit in the CDMA communication system. An instantaneous electric power amount is calculated so as to be compared with a preset upper limit value. When the calculated instantaneous electric power amount exceeds this upper limit value, the correcting unit detects it as an instantaneous peak, and selectively performs an amplitude correction only when the calculated instantaneous electric power amount exceeds the upper limit value so as to reduce distortions of a region located in the vicinity of a region to be corrected.
That is to say, a first aspect of the present invention is featured by such a transmission band limiting filter apparatus equipped with a peak amplitude suppressing function, for performing a transmission band limiting process operation, comprising:
correction unit for calculating a transmission power of a transmission data intersected and comparing the transmission power with a predetermined upper limit with a preset upper limit value in such a manner that when the transmission power exceeds the upper limit value, the transmission power is detected as an instantaneous peak value and correcting the transmission amplitude selectively, prior to filtering in filter unit.
Namely in the present invention, factor of the amplitude limit is not set according to a constant value which is set by outside, amplitude limit is determined according to considering a transmission data and another instantaneous peak value generated by processing the transmission data in the filter unit. And by limiting only necessary part of the transmission data, the transmission band limiting filter apparatus can transmit the data in high reliability without any nonlinear distortion caused by the peak amplitude suppression. Therefore correction is conducted by considering an affect in filer unit, and the corrected date is transmitted into the filter unit. According to the structure, the transmission band limiting filter apparatus can transmit the data in almost all frequency range in high reliability without any nonlinear distortion caused by the peak amplitude suppression.
That is to say, a second aspect of the present invention is featured by such a transmission band limiting filter apparatus equipped with a peak amplitude suppressing function, for performing a transmission band limiting process operation of I-channel transmission data and Q-channel transmission data which is intersected orthogonal to the I-channel transmission data, comprising:
(a) a transmission amplitude calculating unit for calculating a transmission amplitude and transmission power of each of the I-channel transmission data and the Q-channel transmission data intersected orthogonal to the I-channel transmission data;
(b) a transmission power detecting unit for detecting an instantaneous peak value by comparing the transmission power with a preset upper limit value in such a manner that when the transmission power exceeds the upper limit value, the instantaneous peak value appears;
(c) an application range calculating unit for determining an application range of a correction based upon the detection information of the instantaneous peak value detected by the transmission power detecting unit;
(d) a correction value calculating unit for determining an amplitude correction value of the transmission amplitude based on the detection information of the instantaneous peak value;
(e) an enable signal produced by the transmission power detecting unit based upon the appearing timing information of the instantaneous peak value;
(f) a delay line equipped with a correction value function, constituted by a delay line having a correcting unit, for holding both the amplitude correction value supplied from the correction value calculating unit and also the transmission data from which the instantaneous peak value is detected, and for performing the correction in response to the enable signal, the correcting unit correcting the held transmission data based on the amplitude correction value; and
(g) a transmission band limiting filter for executing a band limiting process operation of the transmission data after being corrected, which is obtained from the delay line equipped with the correction value function.
With employment of the above-described arrangement, the transmission band limiting filter apparatus can transmit the data in high reliability without any nonlinear distortion caused by the peak amplitude suppression.
A third aspect of the present invention is featured by such a transmission band limiting filter apparatus equipped with a peak amplitude suppressing function as recited in claim 1 wherein: the transmission amplitude calculating unit is comprised of an electric power calculating unit for calculating instantaneous transmission power based on the output of the transmission amplitude calculating unit; and the transmission power calculating unit owns a data saving function capable of externally setting arbitrary numeral data, and includes: an upper limit value storing apparatus for storing thereinto a power upper limit value; a transmission power comparing unit for comparing the instantaneous transmission power obtained by the electric power calculating unit with the power upper limit value stored in the upper limit value storing apparatus; and a signal converting unit for converting a comparison result obtained by the transmission power comparing unit into the enable signal.
With employment of the above-explained arrangement, in addition to the first effect of the present invention, the transmission band limiting filter apparatus can externally control the upper limit value, and also can perform the adjustment in response to the use condition.
A fourth aspect of the present invention is featured by such a transmission band limiting filter apparatus equipped with a peak amplitude suppressing function as recited in claim 1 wherein:
the correction value calculating unit includes:
(a) a calculating unit for calculating a reciprocal of the instantaneous transmission power entered from the transmission power detecting unit; and
(b) a multiplying unit for multiplying the power upper limit value stored in the upper limit storing apparatus by the calculated reciprocal of the instantaneous transmission power.
With employment of the above-explained arrangement, in addition to the first effect of the present invention, the transmission band limiting filter apparatus can achieve such an effect that the calculation can be readily carried out.
A fifth aspect of the present invention is featured by such a transmission band limiting filter apparatus equipped with a peak amplitude suppressing function as recited in claim 3 wherein:
the application range selecting unit is arranged in such a manner that the correction application range with respect to the transmission data is selected based upon the numeral value entered from the multiplying unit.
A sixth aspect of the present invention is featured by such a transmission band limiting filter apparatus equipped with a peak amplitude suppressing function as recited in claim 1 wherein:
the delay line unit equipped with the correction function includes:
(a) a first selecting unit for selectively switching conditions as to whether or not the transmission data is corrected in correspondence with the numeral value entered from the correction value calculating unit based upon the enable signal entered from the transmission power detecting unit;
(b) a second selecting unit for selectively switching conditions as to whether or not the respective transmission data are separately corrected in response to the application range selection signal entered from the correction value calculating unit;
(c) a delay line constructed of the data saving function capable of saving the transmission data which is used to detect the instantaneous peak value by the transmission power detecting unit; and
(d) a multiplying unit arranged between the data saving function for constituting the delay line and the data saving function, for separately multiplying the outputs of the first and second selecting functions by the transmission data stored in the data saving function.
A seventh aspect of the present invention is featured by such a transmission band limiting filter apparatus equipped with a peak amplitude suppressing function as recited in claim 1 wherein:
the delay line equipped with the correction value multiplying function is arranged by that the transmission data from which the instantaneous peak value has been detected is held, and the multiplication with the amplitude correction value is performed only for a portion of the transmission data which constitutes the subject of the application range.
A eighth aspect of the present invention is featured by such a transmission band limiting filter apparatus equipped with a peak amplitude suppressing function as recited in claim 1 wherein:
the delay line unit equipped with the correction value multiplying function includes:
(a) a selecting unit for selectively switching conditions as to whether or not the transmission data is corrected in correspondence with the correction value entered from the correction value calculating unit based upon the enable signals entered from the transmission power detecting unit and also the transmission amplitude calculating unit;
(b) a delay line constructed of the data saving function capable of saving the transmission data which is used to detect the instantaneous peak values by the transmission power detecting unit and the transmission amplitude calculating unit; and
(c) a multiplying unit arranged between the data saving function for constituting the delay line and the data saving function, for separately multiplying the outputs of the respective selecting functions by the transmission data stored in the data saving function.
An eleventh aspect of the present invention is featured by such a transmission band limiting filter apparatus equipped with a peak amplitude suppressing function as recited in claim 1 wherein:
the transmission amplitude calculating unit and the transmission power detecting unit are further comprised of:
(b) a signal phase changing amount calculating unit for calculating a phase changing amount of an arbitrarily settable signal section based upon the output of the transmission amplitude calculating function; and
(f) a converting unit for converting a comparison result between the phase changing amount detected by the signal phase changing amount detecting unit and the transmission power comparing function into the enable signals.
A tenth aspect of the present invention is featured by such a transmission band limiting filter apparatus equipped with a peak amplitude suppressing function as recited in claim 1 wherein:
the transmission amplitude calculating unit and the transmission power detecting unit are further comprised of:
(b) a signal phase changing amount calculating unit for calculating a phase changing amount of an arbitrarily settable signal section based upon the output of the transmission amplitude calculating function;
(c) a signal amplitude changing amount detecting unit for detecting an amplitude changing amount of an arbitrarily settable signal section based upon the output of the transmission amplitude calculating function; and
(g) a converting unit for converting a comparison result between the phase changing amount detected by the signal phase changing amount detecting unit and the transmission power comparing function into the enable signals.
An eleventh aspect of the present invention is featured by such a transmission band limiting filter apparatus equipped with a peak amplitude suppressing function as recited in claim 1, further comprising:
(f) a transmission power monitoring unit for monitoring a power difference between move averaged transmission power of the transmission data processed by the transmission band limiting filter and set reference power,.and for calculating a power adjusting value based upon the detected power difference; and
(g) a multiplying function unit for multiplying the move averaged transmission power of the transmission data processed by the transmission band limiting filter by the power adjusting value entered from the transmission power monitoring unit.
A twelfth aspect of the present invention is featured by such a transmission band limiting filter apparatus equipped with a peak amplitude suppressing function as recited in claim 1, further comprising:
(f) a transmission power detecting unit for calculating an instantaneous peak value based upon both move averaged transmission power of the transmission data processed by the transmission band limiting filter and also instantaneous transmission power, for calculating a peak difference between the calculated instantaneous peak value and the set reference instantaneous peak value; and for performing a transmission amplitude calculation and transmission power in such a manner that an instantaneous peak value optimized with respect to a transmission analog amplifier connected subsequent to the transmission power detecting unit is again set; and also
an instantaneous peak value monitoring unit for executing a feedback control with respect to the correction value calculating unit.
An thirteenth aspect of the present invention is featured by such a transmission band limiting filter apparatus equipped with a peak amplitude suppressing function as recited in claim 1, further comprising: (f) a transmission quality deterioration monitoring unit for calculating a waveform error on a time axis between a waveform shape of the transmission data processed by the transmission band limiting filter and a shape of a set reference transmission waveform; and for feedback-controlling both the transmission power detecting unit and the correction value calculating unit in order that such a waveform error within a transmission quality deterioration characteristic which is allowable within performance is obtained with respect to a receiver for receiving the transmitted data.
A fourteenth aspect of the present invention is featured by such a transmission apparatus used in the CDMA system for storing a plurality of users within the same frequency range, while employing the spread spectrum system, comprising:
(a) a user monitoring unit for monitoring transmission data corresponding to the plurality of users;
(b) a spread-modulating and data multiplexing unit for spread-modulating each of the transmission data inputted from the user managing unit and also for multiplexing the spread-modulated transmission data;
(c) an input dynamic range limiter unit for suppressing an amplitude peak value of data entered from the spread-modulating and data multiplexing unit, and for controlling an input dynamic range with respect to a band limiting process unit provided at a post stage;
(d) a transmission band limiting filter apparatus equipped with a peak amplitude suppressing function, for executing a transmission band limiting process operation with respect to both I-channel transmission data and Q-channel transmission data intersected orthogonal to the I-channel transmission data, which are entered from the input dynamic range limiter unit;
(e) a D/A converting unit for D/A-converting the transmission data entered from the transmission band limiting filter apparatus equipped with the peak amplitude suppressing function;
(f) an analog post filter for removing a folding data portion which is produced during the D/A converting operation with respect to the transmission data entered from the D/A converting unit;
(g) a quadrature modulator for performing a quadrature modulating operation at an arbitrary frequency with respect to the transmission data entered from the analog post filter;
(h) a transmission analog amplifying unit for amplifying the transmission data entered from the quadrature modulator; and
(i) an antenna for actually transmitting the transmission data entered from the transmission analog amplifying unit.